Why leabe got black mark on it ?

i use 400 watts hps , mh same time and they are one feet away . the temp is 79 .
in flower stage
they about 13 inchs tall
ph 6.8
i dont know what wrong .. any advice ?
whhy leave black and yellow ? thanks

straight up bumble bee bud!

New to this please explain . thanks

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i was just kidding. not sure man . jump in the advance forum and ask a expert. probably your nutes.